I chatted with HMS last night at a Steve Dinan presentation
In the first tests, Scroth/HMS tested the harness with Opel seats from Germany, on which the European tests were completed. The goal was to match the Euro data on the US test rig. Scroth are now awaiting test time with E9X M3 seats and are confident that the harness will pass. They have the hardware ready in anticipation of a successful certification, it is just a matter of getting test time. The harness will clip in similar to previous versions, requiring one connection to the seat hard point by the door and in the rear seat. the other end will clip into the stock belt clip on the seat and a stock buckle in the middle of the back seat.
I had another conversation with them about roll-overs and roll cages. Firstly, they made the point that the BMW OEM system is designed to hold you bolt upright in the seat in an accident. Secondly, if the car flips, you can be exposed up to 10G acceleration, so it is tough to move around anyway. In the tiny minority of "pancake" flips when you land directly on the roof, it wont matter much what restraint you are using. Most roll-overs go via the contact with the A-pillar with injuries being caused by a head or a limb being outside the frame of the car. The harness will actually serve to minimize this movement/position. The rep said he has grown tired of debating this online but clearly stands by the safety of his product.